Heat medium heating apparatus and vehicular air-conditioning system including the same

ABSTRACT

Provided is a heat medium heating apparatus including: a plurality of flat heat exchanger tubes 12; PTC heaters 13 that are respectively incorporated between flat tube parts of the flat heat exchanger tubes 12; a heat exchanger holding member 15 that press-fixes the flat heat exchanger tubes 12 and the PTC heaters 13, from one side of the flat heat exchanger tubes 12 to an inner surface of a casing 11; and a control board 17 that has a surface on which a control circuit 21 is mounted, the control circuit 21 including heat-generating electrical components 20 that control the PTC heaters 13, in which the control board 17 includes heat penetration parts that are formed so as to pass through the control board 17 correspondingly to mounting positions of the heat-generating electrical components 20, and the heat-generating electrical components 20 are mounted so as to be cooled via the heat penetration parts.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on Japanese Patent Application No. 2011-060927, the contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat medium heating apparatus that heats a heat medium using a positive temperature coefficient heater and a vehicular air-conditioning system including the heat medium heating apparatus.

2. Description of Related Art

Vehicular air-conditioning systems applied to an electric car, a hybrid car, and other such cars are generally provided with a heat medium heating apparatus that heats a medium to be heated serving as a heat source for heating equipment, and one of such heat medium heating apparatuses is known to heat a medium using a positive temperature coefficient heater (hereinafter referred to as PTC heater) including a positive temperature coefficient thermistor (hereinafter referred to as PTC element) as a heat generating element. The PTC heater has characteristics of a positive temperature coefficient thermistor. Specifically, the resistance of the PTC heater increases as the temperature thereof rises. The consumed current is thus controlled, and the rise in temperature slows down. After that, the consumed current and the temperature of a heat generating part each reach a saturation region to become stable. That is, the PTC heater can control its own temperature.

With regard to the heat medium heating apparatus as described above, Japanese Unexamined Patent Application, Publication No. 2008-7106 (hereinafter referred to as “JP 2008-7106 A”) proposes the following heat medium heating apparatus. A large number of separating walls are provided in a housing including an inlet and an outlet for a heat medium, and the separating walls divide the inside of the housing into a heating chamber and a circulation chamber for the heat medium. PTC heating elements are inserted and set into a portion that is defined as the heating chamber by the separating walls, so as to come into contact with the separating walls. The PTC heating elements heat the heat medium circulated through the circulation chamber via the separating walls.

In addition, Japanese Unexamined Patent Application, Publication No. 2008-56044 (hereinafter referred to as “JP 2008-56044 A”) proposes the following heat medium heating apparatus having a stack structure. A plate-like PTC heater is formed by providing an electrode plate, an insulating layer, and a heat transfer layer on each surface of a PTC element so as to sandwich the PTC element. A pair of heat medium circulating boxes are respectively stacked on both surfaces of the PTC heater thus formed, and the pair of heat medium circulating boxes each include an inlet and an outlet for a heat medium and are communicated with each other. Further, a board accommodating box that accommodates a control board is provided on an outer surface of one of the heat medium circulating boxes, and a cover is provided on each outermost surface of the stack structure.

In the heat medium heating apparatus proposed in JP 2008-7106 A, the PTC heating elements are inserted and set into the heating chamber defined by the separating walls. Therefore, it is not easy to respectively insert and set the PTC heating elements between the separating walls serving as heat transfer surfaces so as to bring the PTC heating elements into close contact therewith. As a result, the thermal contact resistance between the separating walls and the PTC heating elements increases, and the heat transfer efficiency easily decreases. Meanwhile, if the intervals between the separating walls are narrowed in order to obtain closer contact, the workability of incorporating the PTC heating elements remarkably decreases, resulting in an increase in man-hours.

In addition, in the heat medium heating apparatus proposed in JP 2008-56044 A, the pair of heat medium circulating boxes each including a heat radiating fin are respectively stacked on both the surfaces of the PTC heater, the board accommodating box that accommodates the control board is provided on the outer surface of one of the heat medium circulating boxes, the cover is provided on each outermost surface of the stack structure, and the stack structure is then fixed with bolts. Therefore, the PTC heater and the heat medium circulating boxes can be brought into close contact with each other, and the thermal contact resistance therebetween can be reduced. However, because it is difficult to stack the PTC heaters into a multilayer structure, the planar area thereof increases, and the heat medium circulating boxes and the dedicated board accommodating box need to be provided. These boxes are made by aluminum die casting in view of a heat resistance property, a heat transfer property, and other such properties, resulting in a limited reduction in size and weight as well as high costs.

BRIEF SUMMARY OF THE INVENTION

In order to solve the above-mentioned problems, a heat medium heating apparatus and a vehicular air-conditioning system including the same according to the present invention adopt the following solutions.

That is, a heat medium heating apparatus according to the present invention includes: a plurality of flat heat exchanger tubes each including an inlet header part, a flat tube part, and an outlet header part, the flat heat exchanger tubes each allowing a heat medium to flow thereinto through the inlet header part, circulate through the flat tube part, and then flow to an outside thereof through the outlet header part; PTC heaters that are respectively incorporated between the flat tube parts of the flat heat exchanger tubes stacked on each other; a heat exchanger holding member that presses the flat heat exchanger tubes and the PTC heaters alternately stacked on each other, from one side of the flat heat exchanger tubes toward an inner surface of a casing, to thereby bring the flat heat exchanger tubes and the PTC heaters into close contact with each other; and a control board that has a surface on which a control circuit is mounted, the control circuit including a heat-generating electrical component that controls the PTC heaters. The control board includes a heat penetration part that is formed so as to pass through the control board correspondingly to a mounting position of the heat-generating electrical component, the heat penetration part being made of a highly thermally conductive material, and the heat-generating electrical component is mounted so as to be cooled via the heat penetration part.

Further, according to the heat medium heating apparatus of the present invention, the control board is placed above the heat exchanger holding member, and the heat-generating electrical component is mounted so as to be cooled via the heat penetration part by the heat exchanger holding member functioning as a heat sink.

According to the present invention, the plurality of flat heat exchanger tubes are stacked on each other, and the PTC heaters are respectively incorporated between the flat tube parts thereof. In this state, the flat heat exchanger tubes and the PTC heaters are pressed by the heat exchanger holding member, to be thereby brought into close contact with each other. The control board having the surface on which the control circuit is mounted is placed above the heat exchanger holding member, the control circuit including the heat-generating electrical component that controls the PTC heaters. The control board includes the heat penetration part that is formed so as to pass through the control board correspondingly to the mounting position of the heat-generating electrical component, the heat penetration part being made of the highly thermally conductive material, and the heat-generating electrical component is mounted so as to be cooled via the heat penetration part by the heat exchanger holding member functioning as the heat sink. Hence, the PTC heaters are respectively sandwiched and stacked between the plurality of flat heat exchanger tubes, and the flat heat exchanger tubes and the PTC heaters are pressed by the heat exchanger holding member. As a result, the flat heat exchanger tubes and the PTC heaters can be incorporated in close contact with each other. Accordingly, the thermal contact resistance between the flat heat exchanger tubes and the PTC heaters can be reduced, and the heat transfer efficiency can be increased, so that the performance of the heat medium heating apparatus can be enhanced. Further, because the flat heat exchanger tubes and the PTC heaters are stacked into a multilayer structure, the planar area thereof can be reduced, and the heat exchanger module and even the heat medium heating apparatus can be compactified. In addition, because the control board is provided above the heat exchanger holding member that presses the flat heat exchanger tubes from one side thereof, the heat-generating electrical component mounted on the control board can be efficiently cooled via the heat penetration part by the heat exchanger holding member functioning as the heat sink. Accordingly, easy incorporation of the control board and the reliability thereof against heat can be ensured, and the need to provide a dedicated board accommodating box and a large-sized heat medium circulating box can be eliminated, leading to a reduction in size and weight of the heat medium heating apparatus as well as lower costs thereof.

Further, according to the heat medium heating apparatus of the present invention, in the heat medium heating apparatus having the above-mentioned feature, the heat exchanger holding member is made of an aluminum alloy plate.

According to the present invention, the heat exchanger holding member is made of the aluminum alloy plate. Therefore, heat from the heat-generating electrical component on the control board is transferred through the heat penetration part to the heat exchanger holding member made of the light aluminum alloy plate having excellent thermal conductivity, and the heat is then transferred to the heat exchanger holding member cooled by the flat heat exchanger tubes, whereby the heat-generating electrical component can be cooled. Accordingly, the cooling performance of the heat-generating electrical component mounted on the surface of the control board can be enhanced by the heat exchanger holding member functioning as the heat sink, the reliability against heat can be increased, and the reduction in weight can be retained.

Further, according to the heat medium heating apparatus of the present invention, a spacer member is interposed between the heat exchanger holding member and the heat penetration part of the control board, the spacer member being made of a highly thermally conductive material and having a predetermined thickness.

According to the present invention, the spacer member is interposed between the heat exchanger holding member and the heat penetration part of the control board, the spacer member being made of the highly thermally conductive material and having the predetermined thickness. Therefore, when the control board is placed above the heat exchanger holding member, even if a given interval therebetween needs to be ensured, the spacer member made of the highly thermally conductive material such as an aluminum alloy plate and having the predetermined thickness is interposed therebetween, whereby the heat exchanger holding member can function as the heat sink to thereby reliably cool the heat-generating electrical component mounted on the surface of the control board. Accordingly, even in such a case, the cooling performance for the control board can be enhanced, the reliability against heat can be ensured, and the reduction in weight can be retained.

Further, according to the heat medium heating apparatus of the present invention, a plurality of terminal blocks are arranged along one side of a surface of the control board, and a plurality of terminals extending from one ends of electrode plates provided on both surfaces of the PTC heaters are respectively connectable directly to the terminal blocks.

According to the present invention, the plurality of terminal blocks are arranged along one side of the surface of the control board, and the plurality of terminals extending from one ends of electrode plates provided on both the surfaces of the PTC heaters are respectively connectable directly to the terminal blocks. Therefore, the control board having the surface on which the control circuit including the heat-generating electrical component that controls the PTC heaters is mounted can be electrically connected to the electrode plates provided on both the surfaces of the PTC heaters, by respectively connecting, on the surface side of the control board, the terminals extending from the one ends of the electrode plates directly to the terminal blocks arranged along the one side of the surface of the control board. Accordingly, the work of electrically connecting the control board to the electrode plates can be facilitated, and the assembling properties can be thus improved. Further, the need to provide a harness is eliminated, leading to a reduction in the number of components, more simplified configuration, and lower costs.

Further, according to the heat medium heating apparatus of the present invention, in the heat medium heating apparatus having any of the above-mentioned features, the flat heat exchanger tubes and the PTC heaters in an alternately stacked state are fastened to an inner bottom surface of the casing by the heat exchanger holding member, the casing including a heat medium inlet and a heat medium outlet respectively communicated with the inlet header part and the outlet header part.

According to the present invention, the plurality of flat heat exchanger tubes and the PTC heaters in the alternately stacked state are fastened to the inner bottom surface of the casing by the heat exchanger holding member, the casing including the heat medium inlet and the heat medium outlet respectively communicated with the inlet header part and the outlet header part. Therefore, the flat heat exchanger tubes and the PTC heaters alternately stacked on each other are fastened to the inner bottom surface of the casing by the heat exchanger holding member, whereby the flat heat exchanger tubes and the PTC heaters can be fixed in close contact with each other. Accordingly, the flat heat exchanger tubes and the PTC heaters can be stacked on each other such that the close contact therebetween is easily and reliably increased in the course of the stacking. Hence, the thermal contact resistance between the flat heat exchanger tubes and the PTC heaters can be reduced, the heat transfer performance can be thus increased, and the assembling properties can be improved. In addition, the casing does not necessarily need to be made of an aluminum alloy material having a heat resistance property and a heat transfer property, and may be made of a resin material, leading to a reduction in weight as well as lower costs.

Further, a vehicular air-conditioning system according to the present invention allows a heat medium heated by a given heat medium heating apparatus to circulate through a heat radiator placed in an air flow passage, and includes the heat medium heating apparatus having any of the above-mentioned features as the given heat medium heating apparatus.

According to the present invention, the heat medium heated by the heat medium heating apparatus having any of the above-mentioned features can circulate through the heat radiator placed in the air flow passage. Therefore, the heat medium to be supplied to the heat radiator provided in the air flow passage can be heated by the heat medium heating apparatus having the reduced size, the reduced weight, and the enhanced performance as described above. Accordingly, the air-conditioning performance, particularly, the heating performance of the vehicular air-conditioning system can be enhanced, and the mounting properties of the air-conditioning system onto a vehicle can be enhanced.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is a schematic configuration view of a vehicular air-conditioning system including a heat medium heating apparatus according to a first embodiment of the present invention;

FIG. 2 is an exploded perspective view of the heat medium heating apparatus illustrated in FIG. 1;

FIG. 3 is a plan view of a state where an upper case of the heat medium heating apparatus illustrated in FIG. 2 is removed;

FIG. 4 is an A-A cross-sectional view of the heat medium heating apparatus illustrated in FIG. 3;

FIG. 5 is a front view of a state where flat heat exchanger tubes, PTC heaters, a metal heat exchanger holding member, and a control board are incorporated in the heat medium heating apparatus illustrated in FIG. 2; FIG. 6 is a right side view of a state where the members illustrated in FIG. 5 are partially omitted;

FIG. 7 is a front view of a state where flat heat exchanger tubes, PTC heaters, a metal heat exchanger holding member, and a control board are incorporated in a heat medium heating apparatus according to a second embodiment of the present invention; and

FIG. 8 is a right side view of a state where the members illustrated in FIG. 7 are partially omitted.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiments of the present invention are described with reference to the drawings.

First Embodiment

Hereinafter, a first embodiment of the present invention is described with reference to FIG. 1 to FIG. 6.

FIG. 1 illustrates a schematic configuration view of a vehicular air-conditioning system including a heat medium heating apparatus according to the first embodiment of the present invention. A vehicular air-conditioning system 1 includes a casing 3 that forms an air flow passage 2 for taking in external air or air inside of a chamber, regulating the temperature of the air, and then guiding the air into the chamber.

Inside of the casing 3, a blower 4, a cooler 5, a heat radiator 6, and an air mix damper 7 are sequentially set from the upstream side to the downstream side of the air flow passage 2. The blower 4 suctions the external air or the air inside of the chamber, increases the pressure of the suctioned air, and feeds the air under pressure to the downstream side. The cooler 5 cools the air fed under pressure by the blower 4. The heat radiator 6 heats the air cooled through the cooler 5. The air mix damper 7 adjusts the flow ratio of the amount of air passing through the heat radiator 6 to the amount of air bypassing the heat radiator 6, and mixes the two flows of air downstream thereof, to thereby make temperature-regulated air.

The downstream side of the casing 3 is connected to a plurality of blow-off ports that blow off the temperature-regulated air into the chamber, via a blow-off mode switching damper (not illustrated) and a duct (not illustrated).

The cooler 5 constitutes a refrigerant circuit together with a compressor (not illustrated), a condenser (not illustrated), and an expansion valve (not illustrated), and evaporates a refrigerant adiabatically expanded by the expansion valve, to thereby cool air passing through the cooler 5. The heat radiator 6 constitutes a heat medium circulating circuit 10A together with a tank 8, a pump 9, and a heat medium heating apparatus 10. A high-temperature heat medium (for example, antifreeze liquid) heated by the heat medium heating apparatus 10 is circulated by means of the pump 9, whereby air passing through the heat radiator 6 is heated.

FIG. 2 illustrates an exploded perspective view of the heat medium heating apparatus 10 illustrated in FIG. 1, FIG. 3 illustrates a plan view of a state where an upper case of the heat medium heating apparatus 10 is removed, and FIG. 4 illustrates an A-A cross-sectional view corresponding to FIG. 3.

As illustrated in FIG. 2, the heat medium heating apparatus 10 includes: a box-like casing 11 (in FIG. 2, only a lower case 11A constituting the casing 11 is illustrated, and an upper case constituting the upper half part of the casing 11 is not illustrated); a heat exchanger module 14 in which a plurality of (for example, three) flat heat exchanger tubes 12 and a plurality of PTC heaters 13 are alternately stacked on each other; a heat exchanger holding member 15 that press-fixes the heat exchanger module 14 to the inner bottom surface of the lower case 11A of the casing 11; and a control board 17 that is placed above the heat exchanger holding member 15 via a pair of spacer members 16 and controls the PTC heaters 13.

The casing 11 has a box-like structure divided into two parts, that is, the upper half part and the lower half part, and the upper case (not illustrated) corresponding to the upper half part is fixed with screws to the lower case 11A corresponding to the lower half part, so that the two parts are integrated with each other. The heat exchanger module 14 formed of the flat heat exchanger tubes 12 and the PTC heaters 13, the heat exchanger holding member 15, the pair of spacer members 16, and the control board 17 are accommodated and set in the internal space of the casing 11 configured as described above.

A heat medium inlet 11B and a heat medium outlet 11C are integrally formed in the lower surface of the lower case 11A so as to protrude downward. The heat medium inlet 11B serves to guide a heat medium introduced into the three stacked flat heat exchanger tubes 12, and the heat medium outlet 11C serves to guide the heat medium that has circulated through the flat heat exchanger tubes 12, to the outside. Boss parts 11D (four portions) are integrally formed in the lower surface of the lower case 11A so as to protrude upward, and the boss parts 11D serve to fasten the heat exchanger holding member 15. The lower case 11A is formed of a resin material (for example, PPS) having a linear expansion coefficient close to that of an aluminum alloy material used for forming the flat heat exchanger tubes 12 accommodated and set in the internal space thereof. Note that it is desirable to form the upper case of a resin material similar to that of the lower case 11A.

Further, a power supply harness hole and an LV harness hole (both not illustrated) are opened in the lower surface of the lower case 11A, and leading end parts of a power supply harness 18 and an LV harness 19 are respectively inserted through the power supply harness hole and the LV harness hole. The power supply harness 18 serves to supply electric power to the PTC heaters 13 via the control board 17. The leading end part thereof is bifurcated, and the bifurcated ends can be respectively fixed with screws to two power supply harness terminal blocks 17A provided to the control board 17. In addition, the LV harness 19 serves to transmit signals for control to the control board 17, and the leading end part thereof can be connected through a connector to the control board 17.

The control board 17 controls current application to the plurality of PTC heaters 13 on the basis of a command from an upper control unit (ECU). A control circuit 21 including a plurality of power transistors (heat-generating electrical components) 20 formed of FETs and IGBTs is mounted on a surface of the control board 17. A current application state of the plurality of PTC heaters 13 can be switched by the control circuit 21. Heat penetration parts 22 (see FIG. 4) are provided in the control board 17 so as to pass through the control board 17 correspondingly to at least portions on which the plurality of power transistors 20 as the heat-generating electrical components are mounted, and the heat penetration parts 22 are each made of a highly thermally conductive material such as copper or aluminum.

Then, the plurality of flat heat exchanger tubes 12 are stacked so as to sandwich each of the plurality of PTC heaters 13 from both sides thereof, whereby the heat exchanger module 14 is configured. Each flat heat exchanger tube 12 is configured by press-forming aluminum alloy thin plates to obtain tube materials and placing the tube materials on top of each other. As illustrated in FIG. 4 to FIG. 6, for example, the three flat heat exchanger tubes 12 are stacked in parallel to each other, and the PTC heaters 13 are respectively incorporated between the stacked flat heat exchanger tubes 12, whereby one heat exchanger module 14 is configured.

Each flat heat exchanger tube 12 includes: a flat tube part 12A having a flat shape in cross-section with a thickness of several millimeters; an inlet header part 12B through which the heat medium flows in; and an outlet header part 12C through which the heat medium flows to the outside, the inlet header part 12B and the outlet header part 12C being respectively formed in both end portions of the flat heat exchanger tube 12. A corrugated plate-like fin (not illustrated) is inserted into the flat tube part 12A, to thereby form a plurality of heat medium circulating passages inside of the tube.

The three flat heat exchanger tubes 12 are sequentially stacked in the order of a lower stage, a middle stage, and an upper stage. At both the ends of the flat heat exchanger tubes 12, the inlet header parts 12B are brought into close contact with each other by a seal material such as an O-ring, and the outlet header parts 12C are brought into close contact with each other by a seal material such as an O-ring. Communication holes (not illustrated) formed in the inlet header parts 12B are communicated with each other, and communication holes (not illustrated) formed in the outlet header parts 12C are communicated with each other. The three flat heat exchanger tubes 12 are incorporated onto the inner bottom surface of the lower case 11A in the stacked state or during the sequential stacking. Then, as described later, the three flat heat exchanger tubes 12 are press-fixed to the inner bottom surface of the lower case 11A by the heat exchanger holding member 15 fastened to the boss parts 11D (four portions) of the lower case 11A.

As described above, the PTC heaters 13 are respectively sandwiched between the three flat heat exchanger tubes 12, whereby one heat exchanger module 14 is configured. The plurality of (two) PTC heaters 13 are configured as publicly known by respectively disposing electrode plates 24 on both the upper and lower surfaces of a positive temperature coefficient (PTC) element 23, and are respectively incorporated between the three flat heat exchanger tubes 12 via insulating sheets. The PTC heaters 13 are incorporated onto the inner bottom surface of the lower case 11A in the stacked state or during the sequential stacking between the three flat heat exchanger tubes 12, and are press-fixed to the inner bottom surface of the lower case 11A by the heat exchanger holding member 15 as described above.

Each electrode plate 24 serves to supply electric power to the PTC element 23, and is made of an aluminum alloy plate having a rectangular shape in planar view. The electrode plates 24 are respectively disposed on both the surfaces of the PTC element 23 so as to sandwich the PTC element 23. Specifically, one electrode plate 24 is disposed on the upper surface of the PTC element 23, and one electrode plate 24 is disposed on the lower surface of the PTC element 23. These two electrode plates 24 sandwich the PTC element 23 from the upper and lower sides.

Further, the upper surface of the electrode plate 24 disposed on the upper surface of the PTC element 23 is in contact with the lower surface of one of the flat heat exchanger tubes 12, and the lower surface of the electrode plate 24 disposed on the lower surface of the PTC element 23 is in contact with the upper surface of another one of the flat heat exchanger tubes 12. In the present embodiment, two electrode plates 24 are disposed between the flat heat exchanger tube 12 in the lower stage and the flat heat exchanger tube 12 in the middle stage, and two electrode plates 24 are disposed between the flat heat exchanger tube 12 in the middle stage and the flat heat exchanger tube 12 in the upper stage. That is, totally four electrode plates 24 are disposed.

These four electrode plates 24 each have substantially the same shape as that of the flat tube part 12A of each flat heat exchanger tube 12, and one terminal 24A is integrally provided to a longer side of each electrode plate 24. The terminal 24A is disposed along the longer side of the corresponding electrode plate 24 so as not to overlap with the other terminals 24A when the corresponding electrode plate 24 is stacked. That is, the position of the terminal 24A provided to each electrode plate 24 is shifted by a little amount along the longer side thereof, and the terminal 24A is arranged in series to the other terminals 24A when the corresponding electrode plate 24 is stacked. Each terminal 24A is provided so as to protrude upward. The terminals 24A are respectively connected with screws to a plurality of (four) terminal blocks 17B arranged along one side of the surface of the control board 17.

The three flat heat exchanger tubes 12 and the two PTC heaters 13 are incorporated onto the inner bottom surface of the lower case 11A in the stacked state or during the sequential stacking as described above. Then, the upper surface of the flat heat exchanger tube 12 in the uppermost stage is pressed toward the inner bottom surface of the lower case 11A by the heat exchanger holding member 15 that is fastened with four screws 25 to the boss parts 11D (four portions) of the lower case 11A. As a result, the upper and lower surfaces of the inlet header parts 12B of the respective flat heat exchanger tubes 12 are brought into close contact with each other, the upper and lower surfaces of the outlet header parts 12C thereof are brought into close contact with each other, and the upper and lower surfaces of the flat tube parts 12A thereof are brought into close contact with the upper and lower surfaces of the PTC heaters 13.

In this way, the heat exchanger module 14 is incorporated into the casing 11. The heat medium introduced from the heat medium inlet 11B of the lower case 11A is guided into the flat tube parts 12A from the inlet header parts 12B of the respective flat heat exchanger tubes 12. In the course of circulation through the flat tube parts 12A, the heat medium is heated by the PTC heaters 13 to have higher temperature, and flows into the outlet header parts 12C. The heat medium passes through the heat medium outlet 11C of the lower case 11A to be guided to the outside of the heat medium heating apparatus 10. Then, the heat medium guided to the outside of the heat medium heating apparatus 10 is supplied to the heat radiator 6 via the heat medium circulating circuit 10A (see FIG. 1).

The heat exchanger holding member 15 also functions as a heat sink for cooling the plurality of heat-generating electrical components 20 mounted on the surface of the control board 17, via the heat penetration parts 22 each made of the highly thermally conductive material such as copper or aluminum. The heat exchanger holding member 15 is made of an aluminum alloy plate. The size of the heat exchanger holding member 15 is large enough to cover the upper surface of the flat heat exchanger tube 12 in the uppermost stage. The longitudinal length of the heat exchanger holding member 15 is larger than that of the control board 17. In order to ensure sealing properties around the inlet header parts 12B and the outlet header parts 12C at the time of press-fixing the heat exchanger module 14 formed of the flat heat exchanger tubes 12 and the PTC heaters 13, the heat exchanger holding member 15 is fastened with the screws 25 to the boss parts 11D of the casing 11 at positions passing through the respective central lines of the inlet header parts 12B and the outlet header parts 12C.

The pair of spacer members 16 are interposed in order to avoid interference between the heat exchanger holding member 15 and the control board 17 placed above the upper surface of the heat exchanger holding member 15, when the positions of the screws 25 for fastening the heat exchanger holding member 15 are restricted to the above-mentioned positions. At least one of the pair of spacer members 16 is made of a highly thermally conductive material such as an aluminum alloy plate, the at least one being provided at a position corresponding to the heat-generating electrical components 20 mounted on the control board 17 and being in contact with the heat penetration parts 22. Another one of the pair of spacer members 16 may be made of a resin material or other such material. In order to obtain reliable contact between the heat exchanger holding member 15 and the spacer members 16, as illustrated in FIG. 5, upward convex planar parts 15A may be formed at respective positions of the heat exchanger holding member 15, the respective positions corresponding to the pair of spacer members 16.

The control board 17 is fixed with a plurality of screws 26 to the upper surface of the heat exchanger holding member 15 via the pair of spacer members 16, and the heat penetration parts 22 thereof are provided so as to be brought into contact with the spacer member(s) 16 made of the highly thermally conductive material. Then, the bifurcated ends of the power supply harness 18 are respectively connected to the terminal blocks 17A of the control board 17, and the LV harness 19 is connected through a connector to the control board 17. Further, the terminals 24A extending from the electrode plates 24 of the PTC heaters 13 are respectively connected directly to the terminal blocks 17B. As a result, the control board 17 is incorporated above the heat exchanger holding member 15, and is accommodated and set in the casing 11.

In the state where the control board 17 is accommodated and set in the casing 11, the plurality of heat-generating electrical components 20 such as the power transistors mounted on the surface of the control board 17 are located near the heat medium inlet 11B formed in the lower case 11A, that is, on the inlet header parts 12B side of the plurality of flat heat exchanger tubes 12 constituting the heat exchanger module 14. The heat penetration parts 22 passing through the control board 17 are cooled by the heat exchanger holding member 15 and the spacer member(s) 16 made of the highly thermally conductive material, the two members being cooled by the heat medium that flows into the inlet header parts 12B and has a relatively low temperature before being heated.

In addition, in the heat medium heating apparatus 10, the three flat heat exchanger tubes 12 and the two PTC heaters 13 are sequentially stacked and incorporated one by one onto the inner bottom surface of the lower case 11A of the casing 11 with both the surfaces of the PTC heaters 13 being sandwiched by the insulating sheets (not illustrated), whereby the heat exchanger module 14 is incorporated. After that, the upper surface of the heat exchanger module 14 is pressed by the heat exchanger holding member 15, and the heat exchanger module 14 is fastened to the lower case 11A. Alternatively, the heat exchanger module 14 is subassembled, and then, the subassembled heat exchanger module 14 is incorporated into the lower case 11A. After that, the upper surface of the heat exchanger module 14 is pressed by the heat exchanger holding member 15, and the heat exchanger module 14 is fastened to the lower case 11A. As a result, the flat heat exchanger tubes 12 and the PTC heaters 13 can be incorporated in close contact with each other.

After that, the control board 17 is fixed with screws above the heat exchanger holding member 15 with the spacer members 16 being interposed therebetween, electrical connections are made, and the upper case (not illustrated) is fixed with screws to the lower case 11A so as to cover the structure, whereby the heat medium heating apparatus 10 can be assembled. Then, the heat medium heating apparatus 10 thus assembled is used for heating the heat medium circulated through the heat medium circulating circuit 10A in the following manner. That is, the heat medium flowing into the inlet header parts 12B via the heat medium inlet 11B is circulated through the plurality of flat heat exchanger tubes 12, is heated by the PTC heaters 13, and then is caused to flow to the outside via the outlet header parts 12C and the heat medium outlet 11C.

Next, the heat medium heating apparatus 10 and the vehicular air-conditioning system 1 according to the present embodiment produce the following operations and effects.

The plurality of flat heat exchanger tubes 12 are stacked on each other, and the PTC heaters 13 are respectively sandwiched between the flat tube parts 12A thereof. In this state, the flat heat exchanger tubes 12 and the PTC heaters 13 are pressed against the lower case 11A by the heat exchanger holding member 15 to be fastened to the lower case 11A. Accordingly, the plurality of flat heat exchanger tubes 12 and the plurality of PTC heaters 13 can be incorporated in close contact with each other.

Accordingly, the thermal contact resistance between the flat heat exchanger tubes 12 and the PTC heaters 13 can be reduced, and the heat transfer efficiency can be increased, so that the performance of the heat medium heating apparatus 10 can be enhanced. Further, because the flat heat exchanger tubes 12 and the PTC heaters 13 are stacked into a multilayer structure, the planar area thereof can be reduced, and the heat exchanger module 14 and even the heat medium heating apparatus 10 can be compactified.

In addition, the control circuit 21 including the heat-generating electrical components 20 such as the power transistors that control the PTC heaters 13 is mounted on the surface of the control board 17, and the control board 17 is placed above the heat exchanger holding member 15. The heat penetration parts 22 are provided in the control board 17 so as to pass through the control board 17 correspondingly to the mounting positions of the heat-generating electrical components 20, and the heat penetration parts 22 are each made of the highly thermally conductive material. The heat-generating electrical components 20 are mounted so as to be cooled via the heat penetration parts 22 by the heat exchanger holding member 15 functioning as the heat sink. With this configuration, the heat-generating electrical components 20 mounted on the surface of the control board 17 can be efficiently cooled via the heat penetration parts 22 by the heat exchanger holding member 15 functioning as the heat sink.

Accordingly, easy incorporation of the control board 17 and the reliability thereof against heat can be ensured, and the need to provide a dedicated board accommodating box and a large-sized heat medium circulating box can be eliminated, leading to a reduction in size and weight of the heat medium heating apparatus 10 as well as lower costs thereof.

In addition, the heat exchanger holding member 15 is made of the aluminum alloy plate. Hence, heat from the heat-generating electrical components 20 on the control board 17 is transferred through the heat penetration parts 22 to the heat exchanger holding member 15 made of the light aluminum alloy plate having excellent thermal conductivity, and the heat is then transferred to the heat exchanger holding member 15 cooled by the flat heat exchanger tubes 12, whereby the heat-generating electrical components 20 can be cooled.

Accordingly, the cooling performance of the heat-generating electrical components 20 mounted on the surface of the control board 17 can be enhanced by the heat exchanger holding member 15 functioning as the heat sink, the reliability against heat can be increased, and the reduction in weight can be retained.

In addition, in the present embodiment, the spacer member(s) 16 made of the highly thermally conductive material and having a predetermined thickness are interposed between the heat exchanger holding member 15 and the heat penetration parts 22 on the control board 17. Hence, when the control board 17 is placed above the heat exchanger holding member 15, even if a given interval therebetween needs to be ensured, the spacer member(s) 16 made of the highly thermally conductive material such as the aluminum alloy plate and having the predetermined thickness are interposed therebetween, whereby the heat exchanger holding member 15 can function as the heat sink to thereby reliably cool the heat-generating electrical components 20 mounted on the surface of the control board 17. Accordingly, even in such a case, the cooling performance for the control board 17 can be enhanced, the reliability against heat can be ensured, and the reduction in weight can be retained.

In particular, on the control board 17, the heat-generating electrical components 20 are located on the inlet header parts 12B side of the flat heat exchanger tubes 12, that is, on the side on which the heat medium flows into the heat medium heating apparatus 10, and the heat exchanger holding member 15 and the spacer member(s) 16 made of the highly thermally conductive material, which function as the heat sinks, are cooled by the heat medium having a relatively low temperature before being heated. Accordingly, the heat-generating electrical components 20 can be effectively cooled, and the cooling performance thereof can be enhanced.

Further, in the present embodiment, the plurality of terminal blocks 17B are arranged along one side of the surface of the control board 17, and the plurality of terminals 24A extending from one ends of the electrode plates 24 provided on both the surfaces of the PTC heaters 13 can be respectively connected directly to the terminal blocks 17B. Hence, the control board 17 having the surface on which the control circuit 21 that controls the PTC heaters 13 is mounted can be electrically connected to the electrode plates 24 provided on both the surfaces of the PTC heaters 13, by respectively connecting, on the surface side of the control board 17, the terminals 24A extending from the one ends of the electrode plates 24 directly to the terminal blocks 17B arranged along the one side of the surface of the control board 17. Accordingly, the work of electrically connecting the control board 17 to the electrode plates 24 can be facilitated, and the assembling properties can be thus improved. Further, the need to provide a harness is eliminated, leading to a reduction in the number of components, more simplified configuration, and lower costs.

In addition, the plurality of flat heat exchanger tubes 12 and the two PTC heaters 13 in an alternately stacked state are fastened to the inner bottom surface of the casing 11 (lower case 11A) by the heat exchanger holding member 15, the casing 11 including the heat medium inlet 11B and the heat medium outlet 11C respectively communicated with the inlet header parts 12B and the outlet header parts 12C. Hence, the flat heat exchanger tubes 12 and the PTC heaters 13 alternately stacked on each other are fastened to the inner bottom surface of the casing 11 by the heat exchanger holding member 15, whereby the flat heat exchanger tubes 12 and the PTC heaters 13 can be fixed in close contact with each other.

Accordingly, the flat heat exchanger tubes 12 and the PTC heaters 13 can be stacked on each other such that the close contact therebetween is easily and reliably increased in the course of the stacking. Hence, the thermal contact resistance between the flat heat exchanger tubes 12 and the PTC heaters 13 can be reduced, the heat transfer performance can be thus increased, and the assembling properties can be improved. In addition, the casing 11 does not necessarily need to be made of an aluminum alloy material having a heat resistance property and a heat transfer property, and may be made of a resin material, leading to a reduction in weight as well as lower costs.

In particular, the heat medium inlet 11B for introducing the heat medium and the heat medium outlet 11C for guiding the heat medium to the outside are integrally formed in the lower case 11A. Hence, when the heat medium is supplied to the heat medium heating apparatus 10, a stress applied to the stacked flat heat exchanger tubes 12 can be distributed, and a load put on the flat heat exchanger tubes 12 can be reduced.

In addition, the heat medium that is heated by the heat medium heating apparatus 10 having the reduced size, the reduced weight, and the enhanced performance as described above can be supplied to the heat radiator 6 provided in the air flow passage 2. Accordingly, the air-conditioning performance, particularly, the heating performance of the vehicular air-conditioning system 1 can be enhanced, and the mounting properties of the air-conditioning system onto a vehicle can be enhanced.

Second Embodiment

Next, a second embodiment of the present invention is described with reference to FIG. 7 and FIG. 8.

The present embodiment is different from the first embodiment described above in that the spacer members 16 are omitted. The present embodiment is the same as the first embodiment in the other features, and hence description of the other features is omitted.

In the present embodiment, the control board 17 is placed directly on the upper surface of the heat exchanger holding member 15 such that the screws 25 that fasten the heat exchanger holding member 15 to the boss parts 11D of the lower case 11A do not interfere with the control board 17. In addition, in order to obtain reliable contact between the heat exchanger holding member 15 and the heat penetration parts 22, it is desirable to form the upward convex planar parts 15A at respective positions of the heat exchanger holding member 15, the respective positions corresponding to the heat penetration parts 22 provided in the control board 17.

As described above, in the case where the screws 25 that fasten the heat exchanger holding member 15 do not interfere with the control board 17 at the time of placing the control board 17 on the heat exchanger holding member 15, the pair of spacer members 16 may be omitted, and the control board 17 may be fixed with the screws 26 directly onto the heat exchanger holding member 15. Even in this case, the heat penetration parts 22 of the control board 17 are respectively brought into contact with the convex planar parts 15A of the heat exchanger holding member 15, whereby the heat-generating electrical components 20 can be efficiently cooled by the heat exchanger holding member 15 functioning as the heat sink.

Accordingly, the present embodiment can produce operations and effects similar to those of the first embodiment.

Note that the present invention is not limited to the embodiments described above, and thus can be modified as appropriate within a range not departing from the gist of the present invention. For example, in the embodiments described above, the three flat heat exchanger tubes 12 are stacked on each other, and the PTC heaters 13 are respectively incorporated between the stacked flat heat exchanger tubes 12. It goes without saying that the present invention is not limited thereto and that the number of the stacked flat heat exchanger tubes 12 and the stacked PTC heaters 13 can be increased or reduced. In addition, in the embodiments described above, the casing 11 is made of a resin material, and it goes without saying that the present invention is not limited thereto. 

1. A heat medium heating apparatus comprising: a plurality of flat heat exchanger tubes each including an inlet header part, a flat tube part, and an outlet header part, the flat heat exchanger tubes each allowing a heat medium to flow thereinto through the inlet header part, circulate through the flat tube part, and then flow to an outside thereof through the outlet header part; PTC heaters that are respectively incorporated between the flat tube parts of the flat heat exchanger tubes stacked on each other; a heat exchanger holding member that presses the flat heat exchanger tubes and the PTC heaters alternately stacked on each other, from one side of the flat heat exchanger tubes toward an inner surface of a casing, to thereby bring the flat heat exchanger tubes and the PTC heaters into close contact with each other; and a control board that has a surface on which a control circuit is mounted, the control circuit including a heat-generating electrical component that controls the PTC heaters, wherein the control board includes a heat penetration part that is formed so as to pass through the control board correspondingly to a mounting position of the heat-generating electrical component, the heat penetration part being made of a highly thermally conductive material, and the heat-generating electrical component is mounted so as to be cooled via the heat penetration part.
 2. The head medium heating apparatus according to claim 1, wherein the control board is placed above the heat exchanger holding member, and wherein the heat-generating electrical component is mounted so as to be cooled via the heat penetration part by the heat exchanger holding member functioning as a heat sink.
 3. The heat medium heating apparatus according to claim 1, wherein the heat exchanger holding member is made of an aluminum alloy plate.
 4. The heat medium heating apparatus according to claim 1, wherein a spacer member is interposed between the heat exchanger holding member and the heat penetration part of the control board, the spacer member being made of a highly thermally conductive material and having a predetermined thickness.
 5. The heat medium heating apparatus according to claim 1, wherein a plurality of terminal blocks are arranged along one side of a surface of the control board, and a plurality of terminals extending from one ends of electrode plates provided on both surfaces of the PTC heaters are respectively connectable directly to the terminal blocks.
 6. The heat medium heating apparatus according to claim 1, wherein the flat heat exchanger tubes and the PTC heaters in an alternately stacked state are fastened to an inner bottom surface of the casing by the heat exchanger holding member, the casing including a heat medium inlet and a heat medium outlet respectively communicated with the inlet header part and the outlet header part.
 7. A vehicular air-conditioning system comprising: a heat medium heating apparatus; a heat radiator placed in an air flow passage through which a heat medium heated by the heat medium heating apparatus circulates, wherein the heat medium heating apparatus comprising: a plurality of flat heat exchanger tubes each including an inlet header part, a flat tube part, and an outlet header part, the flat heat exchanger tubes each allowing a heat medium to flow thereinto through the inlet header part, circulate through the flat tube part, and then flow to an outside thereof through the outlet header part; PTC heaters that are respectively incorporated between the flat tube parts of the flat heat exchanger tubes stacked on each other; a heat exchanger holding member that presses the flat heat exchanger tubes and the PTC heaters alternately stacked on each other, from one side of the flat heat exchanger tubes toward an inner surface of a casing, to thereby bring the flat heat exchanger tubes and the PTC heaters into close contact with each other; and a control board that has a surface on which a control circuit is mounted, the control circuit including a heat-generating electrical component that controls the PTC heaters, wherein the control board includes a heat penetration part that is formed so as to pass through the control board correspondingly to a mounting position of the heat-generating electrical component, the heat penetration part being made of a highly thermally conductive material, and the heat-generating electrical component is mounted so as to be cooled via the heat penetration part.
 8. The vehicular air-conditioning system according to claim 7, wherein the control board is placed above the heat exchanger holding member, and wherein the heat-generating electrical component is mounted so as to be cooled via the heat penetration part by the heat exchanger holding member functioning as a heat sink. 